Micro-electromechanical systems (MEMS) devices have been used to control very small components formed on semiconductor substrates. MEMS electrostatic actuators require very low power and potentially fast response. For static response, no current typically flows except due to parasitics. Hence, almost no power is consumed, making electrostatic MEMS actuators ideal for move-and-hold actuators.
Out-of-plane electrostatic actuators usually consist of either a vertical comb drive or a parallel plate capacitor where one of the plates is allowed to move. Vertical comb drives require multiple complex processes to generate electro-mechanical structures in vertically stacked layers using, for example, expensive silicon on insulator (SOI) and deep reactive ion etch (DRIE) processes. In the case of existing parallel plate capacitor-type actuators, a common limitation is “snap down,” where the stable travel distance is limited to around ⅓ of the total plate separation before the movable capacitor plate “snaps down” into contact with the stationary capacitor plate. In addition, both of these types of existing actuators provide a limited range of motion.